1. Field of the Invention
The present invention relates to temperature measurement technology, and more specifically, to a multi-element rake thermocouple. Particular utility for the present invention is found in temperature measurement in turbine engines.
2. Description of Related Art
Rake thermocouple devices are known in the art, and are generally provided as temperature measurement mechanisms for high temperature and/or high air flow environments such as turbine engines. As a general matter, rake thermocouple devices include a plurality of thermocouples arranged at different distances along the length of the rake, and exposed to the airflow in a turbine engine to measure temperature. One such thermocouple is provided in U.S. Pat. No. 5,812,588, issued to Deak et al. The ""588 patent discloses a temperature probe that includes an outer probe tube projecting into the hot-gas region of the waste-gas diffusor, and the probe tube is provided with an inner bore running in the direction of the tube axis of the probe tube. The probe tube includes a number of throughflow ducts over its length running transversely relative to the tube axis and in which are located a number of thermocouples arranged in the throughflow ducts. The thermocouples are connected to a compensating line in a terminal box. Each thermocouple is arranged in a solely heat-movably guided manner in a protective tube which is fixed relative to the inner bore of the probe tube.
One disadvantage of this design is that in order to replace a single defective thermocouple, all the thermocouple units must be removed and replaced. Also, the ""588 patent does not provide any mechanism to dampen stress vibrations that occur in turbine environments.
Accordingly the present invention provides a thermocouple probe assembly that includes ball bushings placed along the length of the assembly to dampen vibrations and thereby reduce mechanical stress on the assembly. A rake thermocouple is provided that includes a plurality of probe tubes arranged parallel to one another, and each probe assembly is placed into an individual probe tube. Each probe tube has a window defined therein, and an air inlet port extending from the window generally perpendicular to the probe tube. The rake also includes a mated end cap and cup bushing having a defined gap between the inside diameter of the cup bushing and the outside diameter of the end cap to further dampen mechanical stress on the rake.
In one aspect, the present invention provides a thermocouple probe assembly that includes a thermocouple tip section comprising a thermocouple junction coupled to a tapered bushing, a ball bushing, and a connecting cable connecting the ball bushing to the thermocouple tip section.
The present invention also provides a thermocouple probe assembly, comprising a thermocouple junction coupled to a ball bushing. The ball bushing is coupled to the thermocouple junction at a predetermined distance from the thermocouple junction. The predetermined distance is chosen to dampen vibration of the thermocouple probe assembly.
In yet another aspect, the present invention provides a thermocouple probe tube, comprising a tubular member having an inside diameter and a long axis; a window formed within the tubular member formed generally perpendicular to the long axis; and an air inlet port extending from the window in at least one direction.
In still another aspect, the present invention provides a rake thermocouple, comprising at least one thermocouple probe assembly comprising a thermocouple junction coupled to a ball bushing; and at least one thermocouple probe tube housing said thermocouple probe, said at least one thermocouple probe tube comprising a tubular member having an inside diameter and a long axis; a window formed within the tubular member formed generally perpendicular to the long axis; and an air inlet port extending from the window in at least one direction.
It will be appreciated by those skilled in the art that although the following Detailed Description will proceed with reference being made to preferred embodiments, the present invention is not intended to be limited to these preferred embodiments. Other features and advantages of the present invention will become apparent as the following Detailed Description proceeds, and upon reference to the Drawings, wherein like numerals depict like parts, and wherein: